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Pressure-sensitive adhesive tape for flexible printed circuit

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Pressure-sensitive adhesive tape for flexible printed circuit


The present invention provides a pressure-sensitive adhesive tape for a flexible printed circuit, from which a release liner can be released without being torn off even after being subjected to a high temperature process such as a solder reflow process. The pressure-sensitive adhesive tape of the present invention includes: a pressure-sensitive adhesive layer; and a release liner on at least one surface of the pressure-sensitive adhesive layer, wherein a tensile strength of the release liner in a machine direction is 50 MPa to 150 MPa, and a tensile strength of the release liner in a machine direction after heating at 280° C. for 5 min is 20 MPa to 120 MPa.

Browse recent Nitto Denko Corporation patents - Osaka, JP
Inventors: Hakaru HORIGUCHI, Noritsugu DAIGAKU, Takahiro NONAKA, Rie KUWAHARA
USPTO Applicaton #: #20120270002 - Class: 428 415 (USPTO) - 10/25/12 - Class 428 
Stock Material Or Miscellaneous Articles > Layer Or Component Removable To Expose Adhesive >Polymer Derived From Material Having At Least One Acrylic Or Alkacrylic Group Or The Nitrile Or Amide Derivative Thereof (e.g., Acrylamide, Acrylate Ester, Etc.)

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The Patent Description & Claims data below is from USPTO Patent Application 20120270002, Pressure-sensitive adhesive tape for flexible printed circuit.

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BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a pressure-sensitive adhesive tape to be used for fixing a flexible printed circuit.

2. Background Art

In electronic devices, wiring circuit boards have been used and, as the wiring circuit boards, flexible printed circuits (referred to as “FPC” in some cases) have been widely utilized. The FPC is usually used in a state of being fixed to a housing of an electronic device or a reinforcing plate (such as an aluminum plate, a stainless plate and a polyimide plate). When the FPC is fixed (laminated) to the housing or the reinforcing plate, a pressure-sensitive adhesive tape is used (see Patent Document 1).

In manufacturing the electronic device, an FPC may be subjected to a high temperature process such as a solder reflow process. When subjected to such a high temperature process, a pressure-sensitive adhesive tape including a release liner may be attached to the FPC. Specifically, examples thereof include a case where one surface of a double-sided pressure-sensitive adhesive tape is protected by a release liner, and the other surface of the double-sided pressure-sensitive adhesive tape is laminated to an FPC, and the FPC with the double-sided pressure-sensitive adhesive tape is subjected to a high temperature process, and then the release liner is released therefrom, and the exposed pressure-sensitive adhesive surface is laminated to the housing.

However, in the case where an FPC to which a pressure-sensitive adhesive tape having a release liner is laminated is subjected to a high temperature process, a problem that the release liner is deteriorated by heat during the high temperature process and thus the release liner is torn off (broken), and the like, occurs. The occurrence of such a problem is significant as the heating temperature in the high temperature process increases.

Patent Document 1: JP 2006-302941A

SUMMARY

OF THE INVENTION

Accordingly, the present invention has been made in an effort to provide a pressure-sensitive adhesive tape for a flexible printed circuit, from which a release liner can be released without being torn off even after being subjected to a high temperature process such as a solder reflow process.

Thus, the present inventors have intensively studied in order to solve the problems. As a result, the inventors have found that a pressure-sensitive adhesive tape for a flexible printed circuit, from which a release liner can be released without being torn off even after being subjected to a high temperature process, can be obtained by preparing a pressure-sensitive adhesive tape including a release liner in which, on at least one surface of a pressure-sensitive adhesive layer, a tensile strength in a machine direction is controlled in a predetermined range, and a tensile strength in a machine direction after heating at 280° C. for 5 min is controlled in a predetermined range, thereby completing the present invention.

That is, the present invention provides a pressure-sensitive adhesive tape for a flexible printed circuit, including: a pressure-sensitive adhesive layer; and a release liner on at least one surface of the pressure-sensitive adhesive layer, wherein a tensile strength of the release liner in a machine direction is 50 MPa to 150 MPa, and a tensile strength of the release liner in a machine direction after heating at 280° C. for 5 min is 20 MPa to 120 MPa.

In the pressure-sensitive adhesive tape for a flexible printed circuit, the release liner preferably includes: a glassine paper or a resin coated paper; and a release treatment layer formed by a silicon-based release agent on at least one surface of the glassine paper or the resin coated paper.

In the pressure-sensitive adhesive tape for a flexible printed circuit, the pressure-sensitive adhesive layer preferably includes, as an essential component, an acrylic polymer formed from a monomer component including an acrylic monomer represented by the following formula (I) in an amount of 50 wt % or more based on an entire monomer component (100 wt %) forming the acrylic polymer:

CH2═C(R1)COOR2  (I)

wherein R1 represents a hydrogen atom or a methyl group, and R2 represents an alkyl group having 4 to 14 carbon atoms.

In the pressure-sensitive adhesive tape for a flexible printed circuit, dimensional change rates of the release liner in both a machine direction and a transverse direction before and after storage for 24 hours under an atmosphere of 60° C. and 90% RH are preferably 2.0% or less.

In the pressure-sensitive adhesive tape, when the pressure-sensitive adhesive tape is cut to have a size of a width of 30 mm and a length of 130 mm, the cut pressure-sensitive adhesive tape is heated at 280° C. for 5 min, and then, the release liner is released from the surface of the pressure-sensitive adhesive layer under the conditions of a release angle of 90° and a tensile speed of 300 mm/min, the release liner can be preferably released from the surface of the pressure-sensitive adhesive layer without being torn off.

In the pressure-sensitive adhesive tape, the silicon-based release agent preferably includes a thermosetting silicon-based release agent.

The pressure-sensitive adhesive tape preferably has a pull tab.

Since the pressure-sensitive adhesive tape for a flexible printed circuit of the present invention has the above configuration, a release liner can be released without being torn off even after being subjected to a high temperature process, and thus, the release liner has excellent release workability. On this account, when the pressure-sensitive adhesive tape for a flexible printed circuit of the present invention is used, productivity or quality of an electronic device having the FPC is improved. In this specification, the “release workability” refers to “easiness of release or easiness of release work” of a release liner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view (plane view) illustrating an example of a state in which the pressure-sensitive adhesive tape for a flexible printed circuit of the present invention having a pull tab is laminated to an adherend.

FIG. 2 is a schematic view (A-A cross-sectional view in FIG. 1) illustrating an example of a state in which the pressure-sensitive adhesive tape for a flexible printed circuit of the present invention having a pull tab is laminated to an adherend.

DETAILED DESCRIPTION

OF THE INVENTION

The pressure-sensitive adhesive tape for a flexible printed circuit of the present invention (hereinafter, simply, referred to as the “pressure-sensitive adhesive tape of the present invention” in some cases) includes a release liner (referred to as the “release liner of the present invention” in some cases), which has a tensile strength in a machine direction of 50 to 150 MPa and a tensile strength in a machine direction after heating at 280° C. for 5 min of 20 to 120 MPa, on at least one side (surface) of a pressure-sensitive adhesive layer. In this specification, the “pressure-sensitive adhesive tape” in principle refers to a pressure-sensitive adhesive tape including a release liner (separator), and “the remaining part in which the release liner is released from the pressure-sensitive adhesive tape” is called an “pressure-sensitive adhesive body” in some cases. A surface of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive body is called an “pressure-sensitive adhesive surface” in some cases. In this specification, the “pressure-sensitive adhesive tape” also includes a sheet type, that is, an “pressure-sensitive adhesive sheet”.

The pressure-sensitive adhesive tape of the present invention may be a double-sided pressure-sensitive adhesive tape in which the release liner of the present invention is provided on at least one pressure-sensitive adhesive surface of a pressure-sensitive adhesive body (double-sided pressure-sensitive adhesive body) with pressure-sensitive adhesive surfaces on both sides thereof, and may be a single-sided pressure-sensitive adhesive tape in which the release liner of the present invention is provided on the pressure-sensitive adhesive surface of a pressure-sensitive adhesive body (single-sided pressure-sensitive adhesive body) with a pressure-sensitive adhesive surface at only one side thereof. Among them, the double-sided pressure-sensitive adhesive tape is preferred from the standpoint of laminating a housing of an electronic device or a reinforcing plate to the FPC.

In the case where the pressure-sensitive adhesive tape of the present invention is a double-sided pressure-sensitive adhesive tape, the release liner of the present invention may be provided on at least one pressure-sensitive adhesive surface of the pressure-sensitive adhesive body and the release liner may not be provided on the other pressure-sensitive adhesive surface. In the case where the release liner of the present invention is provided on one pressure-sensitive adhesive surface of the pressure-sensitive adhesive body (double-sided pressure-sensitive adhesive body) and the release liner is not provided on the other pressure-sensitive adhesive surface (the case of a so-called “single separator type”), a form in which both pressure-sensitive adhesive surfaces of the pressure-sensitive adhesive body are protected with both surfaces of the release liner of the present invention by winding the pressure-sensitive adhesive tape of the present invention in a roll shape may be taken. On the other hand, in the case where release liners are provided on both pressure-sensitive adhesive surfaces of the pressure-sensitive adhesive body (double-sided pressure-sensitive adhesive body), respectively (the case of a so-called “double separator type”), both release liners provided on both pressure-sensitive adhesive surfaces of the pressure-sensitive adhesive body may be a release liner of the present invention, or any one of the release liners may be a release liner other than the release liner of the present invention (hereinafter, referred to as “the other release liner” in some cases).

[Release Liner of the Present Invention]

The tensile strength in a machine direction (referred to as “tensile strength (initial stage) in a machine direction” in some cases) of the release liner of the present invention is 50 MPa to 150 MPa, preferably 60 MPa to 140 MPa, and more preferably 65 MPa to 135 MPa. By controlling the tensile strength (initial stage) in the machine direction to 50 MPa or more, the release liner is not easily torn off during release, and thus, the release workability is improved. On the other hand, the flexibility of the pressure-sensitive adhesive tape may be maintained by controlling the tensile strength (initial stage) in the machine direction to 150 MPa or less, and thus, the workability is improved. Typically, the machine direction of the pressure-sensitive adhesive tape of the present invention (longitudinal direction, MD) (a manufacturing line direction (flow direction) in the manufacturing process of the pressure-sensitive adhesive tape of the present invention) is equal to the machine direction of the release liner of the present invention.

The tensile strength in a machine direction after heating at 280° C. for 5 min (referred to as “tensile strength (after heating) in a machine direction” in some cases) of the release liner of the present invention is 20 MPa to 120 MPa, preferably 30 MPa to 110 MPa, and more preferably 40 MPa to 105 MPa. When the release liner is released, any defects that the release liner is torn off or broken are not caused even after being subjected to a high temperature process by controlling the tensile strength (after heating) in the machine direction to 20 MPa or more, and thus, excellent release workability can be exhibited even after the high temperature process. On the other hand, the flexibility of the pressure-sensitive adhesive tape can be maintained by controlling the tensile strength (after heating) in the machine direction to 120 MPa or less, and thus, the workability is improved.

The tensile strength (initial stage) in the machine direction and tensile strength (after heating) in the machine direction, of the release liner of the present invention, are not particularly limited, but may be controlled by the kind (material) of a liner substrate, the thickness of a liner substrate, the basis weight of a liner substrate, the density of a liner substrate, and the like.

The tensile strength in a transverse direction (referred to as “tensile strength (initial stage) in a transverse direction” in some cases) of the release liner of the present invention is not particularly limited, but is preferably 30 MPa to 120 MPa, and more preferably 35 MPa to 100 MPa. By controlling the tensile strength (initial stage) in the transverse direction to 30 MPa or more, the release liner is not easily torn off during release, and thus, the release workability is improved. On the other hand, the flexibility of the pressure-sensitive adhesive tape may be maintained by controlling the tensile strength (initial stage) in the transverse direction to 120 MPa or less, and thus, the workability is improved.

The tensile strength in a transverse direction after heating at 280° C. for 5 min (referred to as “tensile strength (after heating) in a transverse direction” in some cases) of the release liner of the present invention is not particularly limited, but is preferably 10 MPa to 100 MPa, and more preferably 15 MPa to 90 MPa. When the release liner is released, any defects that the release liner is torn off or broken are hardly caused even after being subjected to a high temperature process by controlling the tensile strength (after heating) in the transverse direction to 10 MPa or more, and thus, the release workability is improved after the high temperature process. On the other hand, the flexibility of the pressure-sensitive adhesive tape can be maintained by controlling the tensile strength (after heating) in the transverse direction to 100 MPa or less, and thus, the workability is improved.

The tensile strength (initial stage) in the transverse direction and tensile strength (after heating) in the transverse direction, of the release liner of the present invention, are not particularly limited, but may be controlled by the kind of a liner substrate, the thickness of a liner substrate, the basis weight of a liner substrate, the density of a liner substrate, and the like.

The tensile strength (tensile strength (initial stage) and tensile strength (after heating) described above can be measured in accordance with JIS P8113. Specifically, the tensile strength can be measured by a method described in “(1) Tensile strength (initial stage) of release liner” and “(2) Tensile strength (after heating) of release liner” in the (Evaluation) as described below.

The dimensional change rate in a machine direction of the release liner of the present invention before and after storage for 24 hours under an atmosphere of 60° C. and 90% RH (referred to as a “dimensional change rate (in a machine direction)” in some cases) is not particularly limited, but is preferably 2.0% or less (for example, 0% to 2.0%), and more preferably 0% to 1.5%. The generation of adhesion failures such as wrinkling, bending and impairment due to a change in dimension after humidification can be prevented by controlling the dimensional change rate (in a machine direction) to 2.0% or less.

The dimensional change rate in a transverse direction of the release liner of the present invention before and after storage for 24 hours under an atmosphere of 60° C. and 90% RH (referred to as a “dimensional change rate (in a transverse direction)” in some cases) is not particularly limited, but is preferably 2.0% or less (for example, 0% to 2.0%), and more preferably 0% to 1.5%. The generation of adhesion failures such as wrinkling, bending, and impairment due to a change in dimension after humidification can be prevented by controlling the dimensional change rate (in a transverse direction) to 2.0% or less.

The dimensional change rate (in a machine direction) and dimensional change rate (in a transverse direction) of the release liner of the present invention are not particularly limited, but may be controlled by the kind (material) of a liner substrate, the thickness of a liner substrate, the basis weight of a liner substrate, the density of a liner substrate, and the like.

The above-described dimensional change rate is a ratio of change in dimension after storage for 24 hours under an atmosphere of 60° C. and 90% RH to the initial dimension (dimension after storage for at least 24 hours under an atmosphere of 23° C. and 50% RH), and is represented by the following equation.

Dimensional Change Rate(%)=(L1−LO)/L0×100

(where, L0 is an initial dimension, and L1 is a dimension after storage for 24 hours under an atmosphere of 60° C. and 90% RH)

The release liner of the present invention is not particularly limited, so long as the tensile strength (initial stage) in the machine direction and the tensile strength (after heating) in the machine direction are controlled within the above-described ranges. Examples of the release liner of the present invention include a release liner in which a release treatment layer is formed on at least one surface of a liner substrate, a low-adhesion release liner including a fluorine-based polymer and a low-adhesion release liner including a non-polarity polymer (for example, an olefin-based polymer, and the like). Among them, from the standpoint of easily controlling the tensile strength or release force of the release liner, the release liner in which the release treatment layer is formed on at least one surface of a liner substrate is preferable. The “liner substrate” in this specification refers to a substrate of the release liner, and is called a “separator base paper” in some cases.

(Liner Substrate)

The liner substrate in the release liner of the present invention is not particularly limited, but various substrates such as, for example, a plastic-based substrate, a paper-based substrate and a fiber-based substrate, may be used. The liner substrate may have any form of a single layer and a multilayer. As the plastic-based substrate, various plastic-based substrates may be properly selected and used, and examples thereof include a polyolefin-based substrate (such as a polyethylene-based substrate and a polypropylene-based substrate), a polyester-based substrate (such as a polyethylene terephthalate-based substrate, a polyethylene naphthalene-based substrate and a polybutylene terephthalate-based substrate), a polyamide-based substrate (such as a so-called “nylon”-based substrate), a cellulose-based substrate (such as a so-called “cellophane”-based substrate), and the like. As the paper-based substrate, various paper-based substrates may be properly selected and used, and examples thereof include Japanese paper, Western paper, high-quality paper, glassine paper, craft paper, Clupak paper, crepe paper, clay-coated paper, synthetic paper, paper in which a resin is coated on the surface of these base papers coated with resin (hereinafter, referred to as “resin coated paper” or “resin coating paper”), and the like. As the fiber-based substrate, various fiber-based substrates may be properly selected and used, and examples thereof include cloth, non-woven cloth, felt, net, and the like. From the standpoint of heat resistance, the paper-based substrate is preferable, and heat-resistant glassine paper and heat-resistant resin coated paper are more preferable among them.

As the liner substrate, heat-resistant resin coated paper is preferable particularly from the standpoint of low deterioration in strength due to heating. The use of the heat-resistant resin coated paper as a liner substrate allows the tensile strength (initial stage) in a machine direction and the tensile strength (after heating) in a machine direction, of the release liner of the present invention, to be easily controlled within the above-described ranges, and makes it difficult to cause defects that the release liner is torn off or broken when released after a high temperature process, and thus, the release workability after a high temperature process is improved.



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stats Patent Info
Application #
US 20120270002 A1
Publish Date
10/25/2012
Document #
13452067
File Date
04/20/2012
USPTO Class
428 415
Other USPTO Classes
428 418
International Class
32B7/06
Drawings
2



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